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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>WebGL2 Triangle</title>
</head>
<body>
<canvas id="canvas" width="500" height="450"></canvas>
</body>
</html>
/*
This is a modified version of code from webgl2fundamentals.org.
Read more here: https://demyanov.dev/past-and-future-html-canvas-brief-overview-2d-webgl-and-webgpu
*/
"use strict";
var vertexShaderSource = `#version 300 es
in vec2 a_position;
in vec4 a_color;
uniform float u_PointSize;
out vec4 v_color;
void main() {
v_color = a_color;
gl_Position = vec4(a_position, 0, 1);
gl_PointSize = u_PointSize;
}
`;
var fragmentShaderSource = `#version 300 es
precision highp float;
in vec4 v_color;
out vec4 outColor;
void main() {
outColor = vec4(v_color);
}
`;
function main() {
const canvas = document.querySelector("#canvas");
const gl = canvas.getContext("webgl2");
if (!gl) {
console.log("Cant get ctx");
return;
}
const vertexShader = createShader(gl, gl.VERTEX_SHADER, vertexShaderSource);
const fragmentShader = createShader(gl, gl.FRAGMENT_SHADER, fragmentShaderSource);
const program = createProgram(gl, vertexShader, fragmentShader);
gl.clearColor(0.1, 0.2, 0.4, 1.0);
gl.clear(gl.COLOR_BUFFER_BIT);
gl.useProgram(program);
/////////////////////////////////////SETTING UP STATE///////////////////////////////////////
const u_PointSize = gl.getUniformLocation(program, 'u_PointSize');
// Uniform for point size
gl.uniform1f(u_PointSize, 100);
// Attribute locations
const a_PositionIndex = gl.getAttribLocation(program, 'a_position');
const a_ColorIndex = gl.getAttribLocation(program, 'a_color');
// Attribute buffers
const a_PositionBuffer = gl.createBuffer();
const a_ColorBuffer = gl.createBuffer();
// Vertex array object (vao)
// This tells WebGL how to iterate your attribute buffers
const vao = gl.createVertexArray();
gl.bindVertexArray(vao);
// Pull 2 floats at a time out of the position buffer
gl.bindBuffer(gl.ARRAY_BUFFER, a_PositionBuffer);
gl.enableVertexAttribArray(a_PositionIndex);
gl.vertexAttribPointer(a_PositionIndex, 2, gl.FLOAT, false, 0, 0);
// Pull 4 floats at a time out of the color buffer
gl.bindBuffer(gl.ARRAY_BUFFER, a_ColorBuffer);
gl.enableVertexAttribArray(a_ColorIndex);
gl.vertexAttribPointer(a_ColorIndex, 4, gl.FLOAT, false, 0, 0);
// Add some points to the position buffer
const positions = new Float32Array([
-0.75, -0.5,
0, 0.5,
0.75, -0.5,
]);
gl.bindBuffer(gl.ARRAY_BUFFER, a_PositionBuffer);
gl.bufferData(gl.ARRAY_BUFFER, positions, gl.STATIC_DRAW);
// Add some points to the color buffer
const colors = new Float32Array([
1.0, 0.0, 0.0, 1.0, // red
0.0, 1.0, 0.0, 1.0, // green
0.0, 0.0, 1.0, 1.0, // blue
]);
gl.bindBuffer(gl.ARRAY_BUFFER, a_ColorBuffer);
gl.bufferData(gl.ARRAY_BUFFER, colors, gl.STATIC_DRAW);
////////////////////////////////////////////////////////////////////////////////////////////
var primitiveType = gl.TRIANGLES;
var offset = 0;
var count = 3;
gl.drawArrays(primitiveType, offset, count);
}
function createShader(gl, type, source) {
const shader = gl.createShader(type);
gl.shaderSource(shader, source);
gl.compileShader(shader);
const success = gl.getShaderParameter(shader, gl.COMPILE_STATUS);
if (success) {
return shader;
}
console.log(gl.getShaderInfoLog(shader));
gl.deleteShader(shader);
return undefined;
}
function createProgram(gl, vertexShader, fragmentShader) {
const program = gl.createProgram();
gl.attachShader(program, vertexShader);
gl.attachShader(program, fragmentShader);
gl.linkProgram(program);
const success = gl.getProgramParameter(program, gl.LINK_STATUS);
if (success) {
return program;
}
console.log(gl.getProgramInfoLog(program));
gl.deleteProgram(program);
return undefined;
}
main();
Also see: Tab Triggers